Doctor for the Day
by NekoShard
Summary: Donatello feels useless in fights and limited due to being a mutant, but when he has a chance encounter with the Doctor himself, things begin to turn around. Donnie ends up traveling with the Doctor to the New York of 2105. He is fascinated by the robot "Companions" that everyone owns and after digging deeper, discovers a dark secret behind the glory of glory of Great New York.
1. Chapter 1

**NekoShard: **_**"Hi! This is my first crossover fic so give this a chance and don't immediately back out of this. I know it should be in the crossover section, but no one ever checks there so I just put it here. :P"**_

**Raph: **_**"Going against the rules? Huh, you may not be a lost cause after all!"**_

**NekoShard: **_**"Shut up. Anyways, enjoy!"**_

Donatello sat alone in his lab, yet again analyzing a sample of mutagen to try and figure out a retro mutagen that would not freeze or cause someone to breakout in the world's worst case of acne. Outside his doors, he could hear space heroes blaring from the TV and Raph shouting over it,

"Hey Leo could you turn it up a bit more? I don't think the construction workers in metro station eight can hear your stupid show."

"Dude, he probably shouldn't do that," Came Mikey's voice. "It might, like, let them know we're down here."

"That was my point, doofus!" Snapped Raph. Donnie could imagine him rolling his eyes.

"Wow, I can't believe that you want to be discovered! I thought that you- OW!"

A sharp smack cut Mikey's words short. Raph must have hit him over the head.

"Shhhhhh! It's just getting good!" Came Leo's voice.

Donnie sighed. Yet again his brothers were enjoying some down time together, relating through pizza, TV, video games, and some brotherly fighting. None of those ever helped him to fit quite right. He was the tallest, the brother with the gapped toothed smile and slightly OCD personality, the one who was introverted and preferred science textbooks to comics. He was the only one who had a crush that he was still really into even though she hated him, and he wasn't the greatest fighter either, that paired with the fact that he disliked causing anyone harm.

With a sigh, Donatello set aside the beaker of congealing "retro-mutagen" in discouragement.

"It's no use, I'll never get this right!"

Suddenly, the door to his lab opened and Leo stood in the doorway saying,

"Hey Donnie, it's time for evening patrol."

"Oh, you're right, I guess time got away from me."

Standing, Donatello joined his brothers as they raced through the sewers and climbed out of the manhole that served as one of their main entrances to the human world above them, New York. Once above ground, they climbed to the roof of one of the houses and began patrolling the streets from above, always on the look out for mutagen canisters, or the Shredder and Kraang's troops. They moved quickly and with a grace that would have surprised most who were only familiar with stereotypical turtles. As they leaped from rooftop to rooftop, the four brothers appeared as little more than darker shadows against an already dark sky. They completed the routine patrol and were about to head back, when Mikey yelled,

"Dudes! Check this out!"

The others were at his side in a flash, ready to fight. They relaxed when they saw yet another empty alleyway. Raph sheathed his Sais and growled,

"Geez Mikey, don't get me excited like that for nothing."

Grinning like a kid, Mikey leaped into the alley and returned with a large flat box.

"Well be excited bros 'cause we have pizza!"

Lifting a slice with an expression close to reverence, Mikey lowered the steaming food towards his mouth. THWACK! A strong blow from Donatello's Bo staff sent the pizza spinning from his brother's hand to land with a wet splat on the rooftop.

"Hey what was that for?"

Donnie returned his weapon to its holder across the back of his shell and said seriously, "Think Mikey! Does it make any sense that fresh, warm pizza in would just happen to be lying on the ground, unguarded and ready for us to eat without any danger?"

Mikey beamed, "Yes!"

"NO!" Snapped Donnie in exasperation. Leo gingerly picked up a piece and examined it closely. He sniffed it and then nibbled the end.

"It seems alright…I wouldn't worry about it Don; the pizza delivery kid comes through here pretty often. He must have dropped this. Look, you can see fresh tire tracks on the ground there."

"What are we waiting for?" Mikey asked, pushing forward, snatching up another slice and taking a huge bite. "Let's eat! You do realize that alleyway pizza is number eight on my top ten favorite types of pizza, right?"

"Didn't know; don't really care. Gimme some of that!"

Raph joined them and tossed his scientific brother a large piece of the food before shoving some in his own mouth. Nervously, Don reexamined the pizza and then smelled it again, something didn't seem right. Underneath the delicious, steamy scent of cheese, sauce, and pepperoni lay a faint, bitter smell. Careful not to swallow anything, Donatello took a small bite and let it rest on his tongue. His suspicions were confirmed; there was a definite unnatural flavor masked by the pizza.

His quickly spat out the small piece of food and then spat twice more to remove as much of whatever it was that had been in the food from his mouth as he could.

"Guys, there is definitely something wrong! I think we walked right into a-"

The shadows around them began to move, seething with Karai's Foot Bots as they formed a ring around the four brothers.

"Trap…" finished Donnie weakly as he drew his weapon once more.

"Aw yeah!" Cheered Raph, "Pizza and a chance to beat up the Foot? Can this night get any better?"

"If we get home safely, yes," replied Leo as he charged the nearest group of robots.

Mayhem erupted on the roof, Mikey was swinging his nunchucks at lightning speed, Leo was serious and deadly with his twin kasawas, Raph was having the time of his life as he tried to knock out as many enemy ninjas as he could, and Donnie was twirling his staff skillfully while trying to determine a possible weakness that could be the Foot Soldiers undoing.

Suddenly Mikey faltered and dropped to his knees groaning, "Dudes, I'm really not feeling so good right now…"

Immediately, Raph and Leo moved to defend their little brother while Donnie knelt by him to see what was wrong.

"Where does it hurt, Mikey?"

"Ugghnn…my stomach…I think I'm gonna hurl…"

As gently as he could, Donnie moved his orange masked brother back against a wall to make it easier to defend him. As he laid his hand against Mikey's forehead, Donatello's arm was roughly jostled by Leo as his eldest brother stumbled back against him, head in his hands.

"Guys we need to get out of here! I'm feeling really…woozy…" Leo trailed off and slumped to the ground, unconscious.

"Aw shell!" Growled Raph, as he blocked a powerful sword stroke with his crossed sai blades. "You'd better find a way to get Leo back in action soon Donnie or we're all going down!"

Donnie stood and began assisting Raph who looked at him in surprise, "You fighting the Foot with your blade out? You sure you can handle it?"

Knocking aside a knife, Donatello snapped, "Thank you for the vote of confidence, Raph! It's good to know you have that much faith in my abilities. Now give me some help!"

The two of them were not accustomed to fighting as a team since Donnie usually fought with Leo and Raph teamed up with Mikey during training, but they managed to avoid major injuries. Suddenly, Raph let out a cry of horror and stumbled back. Donnie quickly moved to his side and put out a hand to steady his elder brother. Raph clumsily groped for something at his belt and then dashed a smoke bomb to the ground.

Donnie blinked and coughed as he waved the smoke away to see the lair before him. Raph was on hands and knees, hands clenched.

"What's wrong, Raph?"

The red masked turtle snarled, "I can't see! What the shell is going on?"

"Wait here," commanded Donatello as he rushed into his lab, returning with several needles. Before Raph could move, He had gathered a sample of his blood and then proceeded to collect a sample of Mikey and Leo's.

"I'm going to analyze this to see if I can find a cure for whatever drug was in that pizza. It shouldn't take too long."

And it didn't, in half an hour, Donatello returned and injected his brothers with the antidote. Mikey came to first, sitting up and grinning as if he had never been in pain. Then Leo woke up and Raph's eyesight returned.

"Nice work Donnie," complimented Leo. "I'm glad that you were here to give us a hand, otherwise tonight might not have ended so well."

Mikey nodded seriously, "Yeah, I might have thrown up all that pizza! I'd feel awful if it was wasted like that!"

Donnie wasn't paying attention and was looking at his note pad while his brothers turned to their TV show.

"It appears that this poison was a weakened form of mutagen, designed to disable the consumer, nothing more. However this shows that it is possible to alter mutagen so that it will not have uncontrollable effects." Excited now, Donnie continued, "If I can analyze this and determine what was used, I might be able to make progress with that retro mutagen! And if I can then turn April's dad back to normal, she might finally listen to me and realize how I-"

Raph turned to look at him in annoyance. "Are you seriously going to talk about April again?"

Donnie was confused, "Yes, why not?"

"Oh no reason aside from the fact that you talk about nothing else! Is _April_ the only reason you're making that retro-mutagen? What about all those other people who've been mutated? Aren't you trying to help them?"

"O-of course, but-"

"Then act like it!" Snarled Raph, shoving his face so that it was right in front of his purple-masked brother, not an easy feat since Donnie was several inches taller. "Quite mooning over April and get your head in the game and start working for others, not just yourself."

Donnie's patience snapped and he grabbed Raph by the shoulders and spun him around yelling, "Oh, and you aren't working to help yourself when you go and get us into every fight imaginable, even if it isn't necessary?"

Raph seemed startled and began to object, but his brother cut him off.

"I know what you think, "Donnie spends all his time in the lab, he can't fight well with that stupid stick, he's got no chance with April!" Well news flash: I have dreams and wishes too! You think people don't understand _you_, Raph?" He jabbed a finger at Raph's plastron. "Well try looking at something from my point of view for once!"

Now looking angry, Raph shoved Donnie away from him roughly, causing his brother's shell to smash up against the wall, "Geez, do us all a favor and shut up, Donnie! I don't wanna hear it!"

As Raph stalked back to where Leo and Mikey sat, staring in stunned amazement at the fight before them, Donnie's hands slowly curled into fists. Then, snatching up his staff and thrusting it roughly into its holder, he stormed out of the Lair and into the sewers, slipping into a hidden sewer line that lead to the surface. Roughly dashing the tears of anger and hurt from his eyes, Donatello ran as fast as he could. He didn't look back.

**NekoShard: **_**"Okay, I am uber excited about this story! I mean, I am combining two of my favorite TV shows and two of my favorite characters, so this should get interesting. Please review if you like it!"**_

**Raph: **_**"And if you don't like it, still review or I'll smash you into a-"**_

**NekoShard: **_**"Yes, thank you Raphael." **__**Covers Raph's mouth**__** "What he means is please tell me what I can do to make it better if you don't like how I wrote this." **_


	2. Chapter 2

**NekoShard: Hello! Second chapter at long last but the Doctor was giving me trouble when I tried to write in his voice, well him and another person. Oh well, I did my best. Review if you like it!**

Donatello moved aside the manhole cover and climbed out into the street above, shoving the metal circle back into place with his foot. His mind was awhirl and he began to walk, not noticing or caring that he was in full view in the middle of the street. Nor did he notice the faintly glowing eyes that watched him from the rooftops and shadows.

Without his meaning to, Donnie's feet took him to April's house. He stood in the street, illuminated by the light that stood at the edge of the sidewalk, and stared at the closed door. Inside that house, April was probably finishing up her homework and eating dinner. Then next day she would be going to school, interacting with other humans, and seeing…seeing her boyfriend. Swallowing hard, trying to remove the lump in his throat, Donnie blinked to clear the tears in his eyes. Suddenly, a faint sound of sparking and sizzling reached his ears and he jumped back just in time as the light flickered out and the lamp post fell to the ground where he had been standing with a crash.

"That was close…" Donnie thought. Suddenly, the lights all along the street went out, even the lights in the houses. "This can't be good."

A robotic noise reached his ears and he drew his weapon. The darkness around him remained, well, dark, but every now and then he caught a glimpse of a red glow, the robotic eyes of Karai's Foot Bots. Shifting his feet slightly, Donnie's left foot stepped awkwardly on the fallen lamppost and he stumbled, looking down to try and steady himself. That was what the Foot had been waiting for. With their target distracted they launched a silent, deadly attack. Donnie barely managed to deflect a ninja star off his staff before he was fighting for his life, knocking blades aside with his staff and jabbing out whenever he had that rare chance.

"Send out an alarm," part of him thought, "Just one button on your phone and your brothers will come and help!" But another part of him resisted. "They don't care! They think you're weak! If you defeat all of these ninja on your own you might gain their respect."

Gritting his teeth, Donnie struck out again and again. His determination never wavered, but he soon came to realize the foolishness of his actions. There were too many Foot ninja for him to defeat alone. Snatching his T-phone from his belt, Donnie was about to press the button to send a distress signal, when it was knocked from his hand and to the ground, stabbed by a throwing knife. At the same moment, one of the ninja knocked Donnie's feet out from under him and he landed hard on his back. As he began to sit up, Donnie froze at the sight of about ten blades pointed at his throat, ready for the signal to kill. More ninja stood ready to help if he somehow managed to break free. Mechanically, the robot that seemed to be functioning as the leader raised his sword in preparation to strike. Unable to defend himself, Donnie threw up an arm in an attempt to shield himself.

The blow never came. Instead a sound of wires short-circuiting reached his ears and he opened his eyes in confusion.

Electricity was arching along the framework of each and every Foot Bot and they shook in spasms of what almost appeared to be pain before collapsing to the ground. A hand was extended to him, a human hand. He looked up in surprise and found himself staring at a man who was looking back at him with a friendly expression. Warily, Donnie took the offered hand and was hoisted to his feet. He looked the man up and down with interest. He was well dressed in a brown pinstriped suit over a blue shirt and black tie. He wore converse and a long brown trench coat that billowed behind him impressively in the wind. He had sideburns and his brown hair was spiked up in the front. He was tucking a slim metal instrument into a pocket on the inside of his coat and didn't seem at all fazed by the fact that he was standing next to a giant mutant turtle.

"Uh thanks," Said Donnie as he picked up his staff before eyeing the man awkwardly and saying, "You…aren't shocked by the way I look?"

The man grinned, "Shocked? No, not much shocks me these days. Lived long enough."

Donnie faced him and cautiously extended his right hand to shake, "Er, I'm Donatello, but most people call me Donnie."

The man shook his hand as comfortably as if he met beings that resembled aliens every day as he mused aloud, "Donatello…I've met him once before. Very nice man, bit on the eccentric side though. Kept trying to build this flying machine-or was that Leonardo? Ah yes, sorry, I'm the Doctor, pleased to meet you!"

Stowing his staff in the sheath on his shell, Donnie asked, "How did you make all of those robots short-circuit at once?"

"You ever hear of cutting off the head of an organization to stop the body? Well that's basically what I did. This one here," The Doctor nudged one of the robots with his foot, "was the one with the ability to give basic orders to the others. I shorted it out and that caused it to send an order to the others to do the same. I only got rid of one, the others self-destructed."

"Wow," Donnie murmured, impressed. He watched as his rescuer crouched next to the lead Foot Bot. A flicker of movement caught his eye and he yelled, "LOOK OUT!"

Donnie lunged forward and stabbed a lone Foot Bot who had crept up behind the Doctor. The light in the robot's eyes went out and it collapsed on the asphalt, its sword falling from its hand. Looking surprised, the Doctor said in a rather casual voice,

"I must have missed that one. Thanks. Now, who exactly are we dealing with that could make such technology? Ooh of course!" The man sounded as though his suspicions had been confirmed. "The Kraang, they always did have a knack for this type of construction. Never could understand how they did it with only those little tentacles, but they were superb manufacturers of sonic devices. But that was before the war…Now, they are reduced in number and in technological intelligence."

Donnie gaped at the Doctor. "How do you know all this? I mean, it was crazy enough that you don't find me weird, but this is amazing! You know so much about the Kraang that I don't know and I've been fighting them with my brothers for over a year now."

The Doctor chuckled, "Fighting them? They always did like to picture themselves as warriors and it looks like they decided to move on that dream. Well, I should be going, I've got lots of work to do before I can move on."

"What kind of work?" Asked Donnie as he followed the Doctor towards an alley.

The man looked over his shoulder at him and said cheerfully, "Boring mechanic work that you most likely wouldn't understand. Now I really must go!"

He vanished into the shadows at the back of the alley. Donnie stared for a moment, but then followed him, driven by his ceaseless curiosity. He winced as he knocked against something hard in the dark and pulled out the small, LED flashlight that he always carried with him, shining it around to illuminate his surroundings. His eyes widened. A tall wooden box painted blue stood before him, the words "Police Public Call Box" were painted around the top on each side. It seemed that the Doctor had entered the box.

"_What on earth is he doing in there?"_ Thought Donatello as he shoved the door open and stepped inside. His mouth fell open in shock at the sight of a huge room, its walls curving to form a sort of dome structure, supported by branchlike pillars. A raised platform was in front of him and at the center was what appeared to be a strange, extraterrestrial engine. Blue-green light shone from it a glass tube rose from the center, glowing with the same light. The Doctor was bent over the engine and was holding several wires together, pointing the same slim device Donnie had seen earlier.

"Right, now that that's fixed all I need to do is reprogram the central computers and the TARDIS will be ready to fly again!" He said triumphantly, glancing over at where the purple masked ninja stood before moving out of sight behind the machine. A moment later he popped his head back around with a look of surprise and confusion. "What are you doing here?!"

Flustered, Donnie gestured behind him at the door and then around him helplessly. "I-I just followed you. You know so much about aliens and I wanted to hear more and-and…this box, it's bigger on the inside."

"Yeah pretty much," agreed the Doctor.

"It makes sense now," Donnie gasped, "You know so much about aliens because you _are_ one!"

"Correct again!" Laughed the Doctor as his fingers flew across keyboard and screen alike, programing the central computers.

Donnie sank down on the stairs, shaking his head in amazement. "I've been fighting aliens all this time, and then my life is saved by one! This is the last thing that I was expecting!"

The Doctor walked over looking thoughtful.

"Well," He drew the word out slightly, "If I recall correctly you saved mine as well."

Donnie looked surprised as if the thought had just occurred to him. "I suppose that I did. It looks like we're even."

"Yes…" the Doctor agreed, "But since you seem so interested in alien life perhaps-"You'll teach me about it?" Cried Donnie, sitting up straight in excitement.

"I would, but I've never seen anyone really learn from just listening. However, they say that seeing is believing, so what do you say to joining me on a trip to a place where I can show you aliens like you'd never imagine."

A grin spread across Donnie's face and he stood up quickly saying, "It would be an honor!"

Beaming, the Doctor ran over to the engine followed closely by his new companion as he explained,

"This ship is called the TARDIS, which stands for Time And Relative Dimensions In Space. We can go to any planet at any time, and I know the perfect place for you to really experience aliens. Now hold down this lever over here and keep your finger on this button so I can hold these over here and-"

The TARDIS jolted violently, nearly throwing both passengers off their feet, and the scraping/humming of the engine began as the Doctor steered his machine through the Time Vortex.

The trip ended with an abrupt bump and a lot of smoke as a part of the engine caught fire. The Doctor grabbed a fire extinguisher and quickly doused the flames. Then, seeing Donnie's concerned face, he smiled and said,

"Don't worry, it's been doing that a lot as of late. I'll be able to fix it in no time. Now, let's go out and see where we are."

Opening the door, the Doctor gestured for Donnie to go first. Holding his breath in excitement, Donnie stepped outside. He was in another alley but the buildings were huge. Donnie gaped up at the towering skyline. He could see a vague resemblance to the New York of his day, but it was hard to imagine the small suburbs becoming so large.

The Doctor poked his soot-streaked head out the door and squinted up at the sky before joining his new companion outside the TARDIS.

"Great New York! The center of intergalactic trade for this century; the year is 2105. Let's take a closer look, shall we?"

Donnie looked at the city with longing, but then shook his head, "Sorry, but I can't. You look human so you can go anywhere, but I'm limited. Since I'm a mutant I'll just freak a lot of people out."

The Doctor stuck his hands in the pockets of his trench coat and raised an eyebrow. "If you were in your time then I'd agree, but nowadays there are plenty of aliens living in Great New York, most looking much more alien than you ever will. People won't look twice!"

After a moment's hesitation, Donnie nodded and stepped up to stand by the Doctor. A broad smile broke across the Time Lord's face and he led the way to the city with a jovial cry of: "Alonz-y, Donnie boy!"

Little did they realize that the shadows were not empty. A pair of bright green eyes watched the two figures as they exited the alleyway before narrowing with suspicion and fading away into the shadows.

**NekoShard: Okay lemme clear something up. This is the 10****th**** Doctor and it happens between Martha and Donna. I made this to be sort of like the 2003 "Fast Forward" series but with some changes. Well, enjoy!**


End file.
